Molly McNinch’s students continue to work with each other. She challenges a group to consider and articulate the relationships between slant height, width of diameter, and roll radius.

9th Grade Math - Modeling through Geometry: Circumference of a Cup’s Roll*Molly McNinch, Woodside High School, Sequoia Union High School District, Woodside, California*

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In group work, you can see the mathematical practices. The first math practice I see is students working toward understanding. Then the sixth math practice gets at the detail. So if you persevere and get your answer and it's wrong, you can go back into your problem and see “Where did I make my mistake?” That’s what I try to focus on with the students who make a mistake: sometimes students will make their mistake because negative one plus two is not negative three.